1. Field of the Invention
The present invention relates to an apparatus and to a method for the continuous, non-destructive testing for leaks in generally hermetically-sealed, flexible packages, and more particularly relates to an apparatus and method which is adapted to rapidly detect leakages in vacuum from a plurality of packages contained within a closed case, to ascertain the location of the defective package or packages within the case and to automatically divert the case containing the defective package to a location other than that receiving cases containing all acceptable packages.
2. Discussion of the Prior Art
A large assortment of commercially sold products are packaged in hermetically-sealed, flexible packages under an internal vacuum which is adapted to preserve the freshness and condition of the product over a considerable length of time when stored in warehouses and even when displayed in retail outlets. Among such products, particularly in the food industry, wherein a relatively long shelf life is required, may be coffee, products such as dry flavoring additives and other similar comestibles which, when exposed to the atmosphere for any appreciable period of time, will rapidly deteriorate or even decompose, and thereby rendered unsaleable. Consequently, in order to extend the shelf life of such products over lengthy periods of time, they are adapted to be packaged in socalled vacuum packs, or hermetically-sealed packages of impermeable material of a generally flexible nature, wherein the product and vacuum present within each package will impart a certain stiffness or rigidity to the package walls. However, such vacuum-packed flexible packages may occasionally develop leaks, possibly due to porosities in the packaging materials, or because of improper sealing upon evacuation of the packages subsequent to filling thereof with product. Generally, a defective package which is subject to leakage will allow most of the leakage, possibly up to 98% of the vacuum in the package to be detected within a short period of a few hours after the sealing of the package, and in many instances the leakage or defective package can be even detected within minutes of the packaging and sealing procedures.
Although numerous apparatuses and methods have been developed in the packaging industry for detecting leakages, in a non-destructive manner, in flexible hermetically-sealed packages which are under a vacuum or internal pressure, the prior art fails to provide an automatic apparatus for the rapid leakage testing of vacuum-packed flexible packages, and to be able to divert such defective packages in an automatic manner from a series of advancing cases each containing a plurality of the vacuum-packed flexible packages.
Thus, the different kinds of apparatuses and methods which are presently employed in the non-destructive testing of hermetically-sealed packages, particularly in the food industry, do not contemplate the provision of an automatic system for detecting "soft" packages or, in essence, packages subject to leakage, which are located within closed cases adapted to be conveyed to a leakage testing apparatus and in which leaking or defective packages can be detected and identified practically instantaneously, and the case containing the defective package or packages be automatically diverted to a specific location, whereas cases containing all properly hermetically-sealed, and non-leaking packages are conveyed along for palletizing and shipping.
Cassidy U.S. Pat. No. 4,024,956 discloses a method and an apparatus for detecting leaks in flexible packages which are conveyed in sequence along a predetermined linear feed path. In this instance, the packages are subjected to the weights of rollers which, if the rollers are displaced beyond a predetermined extent due to the package being too soft as a result of a leakage of vacuum from the package, a signal will be triggered to indicate the presence of leakage in that package and to allow the package to be manually removed from the continuous package flow. There is no provision in this prior art method and apparatus for the simultaneous leakage testing of a plurality of flexible packages which are arranged within a case and for automatically removing a case containing defective packages from a continuous conveyor feed system while facilitating the continued advance of tested cases which do not contain defective or leaking packages.
Prakken U.S. Pat. No. 4,148,213 discloses an apparatus for detecting and discarding sealed packages which are subject to leaks from a series of sequentially advancing product-filled sealed packages while being transported on a conveyor belt. In this prior art device, pressure is applied to the entire upper surface of the package and, responsive to downward displacement of a pressure piston beyond a predetermined distance, the defective package may then be laterally ejected by the action of a suitable blower arrangement from the path of conveyance of the packages into a reject bin or receptacle. There is no disclosure of an apparatus for the simultaneous testing for leakage of a plurality of vacuum-packed flexible package which are arranged within a closed case and for automatically diverting the case containing such defective packages from the normal flow or transport of further advancing cases containing only satisfactorily sealed packages.
Browning U.S. Pat. No. 3,441,132 relates to a system for detecting the presence or, alternatively, the absence of a required vacuum or pressure within hermetically-sealed containers, in which a wall segment of each container, while the container is being transported along a conveyor belt, is deflected by a magnetic field pulse and the resultant internal pressure-dependent dynamic displacement of the container wall is detected through the intermediary of an electrostatic sensor. An electrical signal generated by the sensor will indicate the presence (or absence) of internal pressure within the container and thereby allow for detection of any leakage therefrom. There is no provision of an automatic apparatus and method for detecting leakages in a non-destructive manner in a plurality of vacuum-sealed, flexible packages contained within a case and for diverting any such case from its normal path of conveyance upon the detection of defective packages therein.
Finally, Haas U.S. Pat. No. 3,751,972 discloses a leakage detector arrangement for testing a sealed container which is constituted of a semi-rigid or flexible material. Each container is individually placed into a pressurizable chamber and the physical container condition is sensed for the generating of a signal representative of the container dimension which would vary in response to the internal pressure present within the container. This rather rudimentary apparatus is not adapted to be utilized in connection with an automatic system for simultaneously, non-destructively testing the "softness" or leakage of vacuum-packed flexible packages which are arranged within a case, and for automatically diverting cases containing any defective packages from a continuous flow of advancing cases.
In essence, none of the prior art publications provide for automatic equipment adapted to check the softness of flexible vacuum-sealed packages which are arranged within a closed case, and for automatically diverting the case with the defective package or packages therein from a conveyor system transporting cases containing all satisfactorily sealed packages.